In the flat panel display device, the thin film transistor liquid crystal display (briefly TFT-LCD) is characterized by small volume, low energy consumption, relatively low manufacturing cost, and no irradiation, and dominates in the current flat panel display market.
Currently, the structure of TFT-LCD mainly includes aligned array substrate and color film substrate (CF), wherein, the color film substrate primarily comprises a glass substrate, a black matrix (briefly BM), a color filter and a protective film. Generally, the black matrix is arranged between the colored patterns formed from color filter in the form of grid, stripes or flecks. The primary function of the black matrix is to increase the contrast of the picture by inhibiting the blending between colors. It can also shield scattered light to prevent malfunction of TFT caused by light leakage among pixels. The primary function of the color filter is to generate three primary colors, i.e., red, green, and blue, by filtering light, and blend the three primary colors—red, green and blue in different intensity ratios, thereby exhibiting different colors and enabling the TFT-LCD to display full colors.
Currently, there are many methods for manufacturing the color filter. However, considering economic benefit, manufacturing stability, and the functional requirements of the color filter, such as color saturation, resolution, and the like, the common techniques include staining methods, pigment dispersion methods, printing methods, as well as electrodeposition methods. Among these, the pigment dispersion method becomes the primary method for preparing the color filter due to the advantages such as high color purity, high precision, high resolution possessed by the thus-prepared color filter.
The basic principle for the pigment dispersion method is to coat a color photoresist on a transparent underlying substrate, then irradiate the coating with ultraviolet light or similar light to form a cured color filter. The color photoresist comprises a pigment dispersion solution which primarily comprises a colored pigment, a dispersing agent, a resin and a solvent. The colored pigment in the pigment dispersion solution can decide the color of the color filter finally formed.
The stability of the pigment dispersion solution is very important. However, the pigment dispersion solution known by persons skilled in the art often has the problem of poor stability. The pigment particles in the pigment dispersion solution are prone to deposition, or even agglomeration. This will directly result in the color film substrate having an uneven surface of the color filter layer, an uneven coating of the color filter layer, thereby causing adverse effect such as light leakage of the color film substrate to occur. Embodiments of the invention aim to provide a pigment dispersing agent that can improve the stability of the pigment dispersion solution, and a process for manufacturing the same.